Wireless power transmitting apparatus and wireless power receiving apparatus

ABSTRACT

A wireless power transfer system is disclosed. A wireless power transmitting apparatus for wirelessly transmitting power to a wireless power receiving apparatus includes a transmitting coil for transmitting the power, a hall sensor for sensing a change width of flux density caused by the wireless power receiving apparatus, and a controller for comparing the sensed change width of the flux density with a predetermined critical value to determine whether to transmit the power, wherein magnets provided in the wireless power transmitting apparatus and the wireless power receiving apparatus are disposed such that polarities of the magnets are different from each other at opposite faces thereof. In the wireless power transfer system, the magnets having polarities are disposed in the wireless power transmitting apparatus and the wireless power receiving apparatus.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.14/606,613, filed on Jan. 27, 2015, (now U.S. Pat. No. 9,912,168 B2,issued on Mar. 6, 2018), which claims priority under 35 U.S.C. § 119 toU.S. Provisional Application No. 61/932,258, filed in the U.S. on Jan.28, 2014, all of which are hereby incorporated by reference into thepresent application.

TECHNICAL FIELD

Embodiments relate to wireless power transfer. More specifically,embodiments relate to a wireless power transmitting apparatus capable ofwirelessly transmitting electric energy and a wireless power receivingapparatus capable of wirelessly receiving electric energy.

BACKGROUND

With rapid development of information communication technology in recentyears, we are moving toward a ubiquitous society based on theinformation communication technology.

In order to access information communication devices anytime anywhere,it is necessary to install sensors each having a computer chip capableof performing a communication function in all social facilities.Consequently, the supply of power to the devices and sensors is a newissue. In addition, as kinds of portable devices, such as a mobilephone, a Bluetooth headset, and an iPod music player, have beenincreased, it takes time and efforts for users to charge batteries. Inrecent years, wireless power transfer has attracted attention as amethod of solving this problem.

Wireless power transmission or wireless energy transfer refers to atechnology of wirelessly transferring electric energy from a transmitterto a receiver using a principle of magnetic induction. In the 1800's, anelectric motor or a transformer employing a principle of electromagneticinduction had been used, and afterward a method for transmittingelectric energy by emitting electromagnetic waves, such as radio wavesor lasers, has been attempted. Actually, electrical toothbrushes orelectrical razors, which are frequently used in daily life, are chargedbased on the principle of electromagnetic induction.

Wireless energy transfer schemes used until now may be divided into amagnetic induction scheme, an electromagnetic resonance scheme, and apower transfer scheme using a short-wavelength radio frequency.

The magnetic induction scheme is a technology using a phenomenon inwhich when two coils are disposed adjacent to each other and current issupplied to one of the coil, a magnetic flux is generated and, as aresult, electromotive force is generated in the other coil. The magneticinduction scheme is being rapidly commercialized for small-sizeddevices, such as a mobile phone. The magnetic induction scheme has anadvantage in that it is possible to transfer power of a maximum ofseveral hundreds of kilowatts (kW) with high efficiency. However, themagnetic induction scheme has a disadvantage in that the maximumtransfer distance is 1 cm or less and thus coils must be disposedadjacent to a charger or the bottom of a mobile phone.

The electromagnetic resonance scheme is characterized by using anelectric field or a magnetic field instead of utilizing anelectromagnetic wave or current. The electromagnetic resonance schemehas an advantage in that the electromagnetic resonance scheme is notaffected by the electromagnetic wave and is thus safe for otherelectronic devices and human bodies. However, the electromagneticresonance scheme has a disadvantage in that the electromagneticresonance scheme is utilized within a limited distance and space andenergy transfer efficiency is somewhat low.

The short-wavelength wireless power transfer scheme, simply an RFscheme, utilizes that energy can be directly transmitted and received ina radio wave form. This technology is an RF wireless power transferscheme using a rectenna. Rectenna, which is a compound word of anantenna and a rectifier, means an element for directly converting RFpower into DC power. That is, the RF scheme is a technology ofconverting an AC radio wave into DC. In recent years, research has beenactively conducted on commercialization of the RF scheme withimprovement in efficiency of the RF scheme.

Wireless power transfer may be variously utilized in various industries,such as IT, railway, and electric home appliance industries as well as amobile industry.

Particularly, magnets may be provided in a wireless power transmitterand a wireless power receiver such that the transmitter can sense thereceiver. The transmitter may sense a magnetic field of the receiver todetermine whether to supply power to the receiver.

Conventionally, however, it is not possible for the transmitter toeffectively sense the magnetic field of the receiver.

SUMMARY

Embodiments provide a wireless power transmitting apparatus, a wirelesspower receiving apparatus, and a wireless power transfer system usingthe same.

Further, embodiments provide a wireless power transmitting apparatuscapable of effectively sensing a magnetic field of a receiver magnet ina wireless power transfer system.

Further, embodiments provide a wireless power transfer system capable ofmore effectively sensing a change of flux density using polarities ofmagnets.

Further, embodiments provide a wireless power transfer system capable ofoptimizing arrangement between a transmitter and a receiver necessaryfor wireless power transfer using polarities of magnets.

Further, embodiments provide a method of arranging polarities of atransmitter magnet and a receiver magnet to more effectively sense amagnetic field of the receiver magnet required to start wireless powertransfer.

It should be noted that objects of the disclosure are not limited to theobjects as mentioned above, and other unmentioned objects of thedisclosure will be clearly understood by those skilled in the art towhich the disclosure pertains from the following description.

Embodiments provide a wireless power transmitting apparatus, a wirelesspower receiving apparatus, and a wireless power transfer system usingthe same.

Further, embodiments provide a method of arranging polarities of atransmitter magnet and a receiver magnet to more effectively sense amagnetic field of the receiver magnet required to start wireless powertransfer and a method of controlling the transmitter and the receiver tobe rapidly arranged for wireless transfer using the same.

In one embodiment, a wireless power transmitting apparatus forwirelessly transmitting power to a wireless power receiving apparatusincludes a transmitting coil for transmitting the power, a hall sensorfor sensing a change width of flux density caused by the wireless powerreceiving apparatus, and a controller for comparing the sensed changewidth of the flux density with a predetermined critical value todetermine whether to transmit the power, wherein magnets provided in thewireless power transmitting apparatus and the wireless power receivingapparatus are disposed such that polarities of the magnets are differentfrom each other at opposite faces thereof.

In another embodiment, a wireless power receiving apparatus forwirelessly receiving power from a wireless power transmitting apparatusincludes a receiving coil for receiving the power and a second magnetfor generating flux density having a predetermined intensity at one sideof a face thereof opposite to the wireless power transmitting apparatus,wherein a first magnet provided in the wireless power transmittingapparatus and the second magnet are disposed such that polarities of themagnets are different from each other at opposite faces thereof.

The above aspects of the disclosure are merely some of the preferredembodiments and various embodiments into which the technical featuresare incorporated may be derived and understood by those skilled in theart from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

Arrangements and embodiments may be described in detail with referenceto the following drawings in which like reference numerals refer to likeelements and wherein:

FIG. 1 is a view illustrating a wireless power transfer system accordingto an embodiment;

FIG. 2 is an equivalent circuit diagram of a transmitting induction coilaccording to an embodiment;

FIG. 3 is an equivalent circuit diagram of a power source and a wirelesspower transmitting apparatus according to an embodiment;

FIG. 4 is an equivalent circuit diagram of a wireless power receivingapparatus according to an embodiment;

FIG. 5 is a perspective view showing a wireless power transfer systemaccording to an embodiment;

FIG. 6 is a perspective view showing the back of a terminal of FIG. 5;

FIG. 7 is a sectional view showing a wireless power transfer systemaccording to an embodiment;

FIG. 8 is a block diagram of a wireless power transfer system accordingto an embodiment;

FIG. 9 is a flowchart illustrating an operation method of a wirelesspower transfer system according to an embodiment;

FIG. 10 is a view showing a voltage signal detected by a hall sensorbased on the distance between a cradle and a terminal;

FIG. 11 is a view showing that a second magnet is disposed in a woundcoil structure;

FIG. 12 is a view showing that a second magnet is disposed in a leadframe coil structure;

FIG. 13 is a view showing flux density based on disposition of thesecond magnet in the lead frame coil structure;

FIG. 14 is a view illustrating a polarity arrangement method ofpermanent magnets provided in a wireless power transmitting apparatusand a wireless power receiving apparatus according to an embodiment;

FIG. 15 is a view illustrating a magnetization method of magnets appliedto a wireless power transmitting apparatus and a wireless powerreceiving apparatus according to an embodiment;

FIG. 16 is a view illustrating a polarity arrangement method of a firstmagnet and a second magnet in a case in which a magnet applied to anembodiment is magnetized using a sectional and outer circumferentialmagnetization method; and

FIG. 17 is a view showing internal components of a wireless powertransmitting apparatus according to another embodiment.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to the preferred embodiments,examples of which are illustrated in the accompanying drawings. Thesuffixes “module” and “unit” of elements herein are used for convenienceof description and thus can be used interchangeably and do not have anydistinguishable meanings or functions.

It will be understood that when an element is referred to as being ‘on’or ‘under’ another element, it can be directly on/under the element, andone or more intervening elements may also be present. When an element isreferred to as being ‘on’ or ‘under’, ‘under the element’ as well as ‘onthe element’ can be included based on the element.

In the description of embodiments, a wireless power transmittingapparatus constituting a wireless power transfer system will also bereferred to as a transmitter, a transmission end, a transmittingapparatus, a transmission side, or a power transmitting apparatus forthe convenience of description. In addition, a wireless power receivingapparatus will also be referred to as a receiver, a terminal, areceiving side, a receiving apparatus, or a power receiving apparatusfor the convenience of description.

A transmitter according to an embodiment may be configured in the formof a pad or a cradle. A transmitter may include a plurality of wirelesspower transmitting means, which may wirelessly transmit to a pluralityof receivers.

A receiver according to an embodiment may be used in a mobile phone, asmart phone, a laptop computer, a terminal for digital broadcasting, apersonal digital assistant (PDA), a portable multimedia player (PMP), anavigation system, an MP3 player, and other small electronic devices.However, the disclosure is not limited thereto. The receiver may be anydevice having a wireless power transmitting means for charging a batterymounted therein. FIG. 1 is a view illustrating a wireless power transfersystem according to an embodiment.

Referring to FIG. 1, the wireless power transfer system may include apower source 100, a wireless power transmitting apparatus 200, awireless power receiving apparatus 300, and a load 400.

In an embodiment, the power source 100 may be included in the wirelesspower transmitting apparatus 200. However, the disclosure is not limitedthereto.

The wireless power transmitting apparatus 200 may include a transmittinginduction coil 210 and a transmitting resonance coil 220.

The wireless power receiving apparatus 300 may include a receivingresonance coil 310, a receiving induction coil 320, and a rectifier 330.

Both ends of the power source 100 may be connected to both ends of thetransmitting induction coil 210.

The transmitting resonance coil 220 may be apart from the transmittinginduction coil 210 by a predetermined distance.

The receiving resonance coil 310 may be apart from the receivinginduction coil 320 by a predetermined distance.

Both ends of the receiving induction coil 320 may be connected to bothends of the RECTIFIER 330. The load 400 may be connected to both ends ofthe rectifier 330. In an embodiment, the load 400 may be included in thewireless power receiving apparatus 300.

Power generated by the power source 100 may be transferred to thewireless power transmitting apparatus 200. The power transferred to thewireless power transmitting apparatus 200 may be transferred to thewireless power receiving apparatus 300 resonating with the wirelesspower transmitting apparatus 200, i.e. having the same resonancefrequency value as the wireless power transmitting apparatus 200, due toa resonance phenomenon.

Hereinafter, a power transfer process will be described in more detail.

The power source 100 may generate AC power having a predeterminedfrequency and transfer the generated AC power to the wireless powertransmitting apparatus 200.

The transmitting induction coil 210 and the transmitting resonance coil220 may be inductively coupled with each other. That is, AC current maybe generated in the transmitting induction coil 210 due to the AC powersupplied from the power source 100. Due to electromagnetic inductionbased on such AC current, the AC current may also be induced in thetransmitting resonance coil 220, which is physically spaced apart fromthe transmitting induction coil 210.

Subsequently, the power transferred to the transmitting resonance coil220 may be transferred to the wireless power receiving apparatus 300having the same resonance frequency value as the wireless powertransmitting apparatus 200 using a frequency resonance scheme due toresonance.

Power may be transferred between two LC circuits, impedances of whichare matched with each other, due to resonance. Power transfer based onresonance may transfer power to a longer distance with higher transferefficiency than that based on an electromagnetic induction scheme.

The receiving resonance coil 310 may receive the power transferred fromthe transmitting resonance coil 220 using the frequency resonancescheme. AC current may flow in the receiving resonance coil 310 due tothe received power. The power transferred to the receiving resonancecoil 310 may be transferred to the receiving induction coil 320inductively coupled with the receiving resonance coil 310 due toelectromagnetic induction. The power transferred to the receivinginduction coil 320 may be rectified by the rectifier 330 and thentransferred to the load 400.

In an embodiment, the transmitting induction coil 210, the transmittingresonance coil 220, the receiving resonance coil 310, and the receivinginduction coil 320 may have a spiral structure or a helical structure.However, the disclosure is not limited thereto.

The transmitting resonance coil 220 and the receiving resonance coil 310may be resonantly coupled with each other such that power can betransferred at a resonance frequency.

The efficiency of power transfer between the wireless power transmittingapparatus 200 and the wireless power receiving apparatus 300 may begreatly improved due to resonant coupling between the transmittingresonance coil 220 and the receiving resonance coil 310.

In the wireless power transfer system as described above, power transferis performed based on the frequency resonance scheme.

In an embodiment, power transfer may be performed based on anelectromagnetic induction scheme in addition to the frequency resonancescheme.

That is, in a case in which the wireless power transfer system performspower transfer based on electromagnetic induction, the transmittingresonance coil 220 included in the wireless power transmitting apparatus200 and the receiving resonance coil 310 included in the wireless powerreceiving apparatus 300 may be omitted.

In wireless power transfer, a quality factor and a coupling coefficientmay be important. That is, power transfer efficiency may be proportionalto the quality factor and the coupling coefficient. As at least oneselected from between the quality factor and the coupling coefficient isincreased, therefore, power transfer efficiency may be improved.

The quality factor may indicate an index of energy that can beaccumulated near the wireless power transmitting apparatus 200 or thewireless power receiving apparatus 300.

The quality factor may vary based on an operating frequency w, theshape, dimension, and material of a coil, etc. The quality factor may berepresented by Equation 1.Q=w*L/R  [Equation 1]

Where L indicates inductance of a coil and R indicates resistancecorresponding to power loss quantity caused in the coil.

The quality factor may have a value of 0 to infinity. As the qualityfactor is increased, the efficiency of power transfer between thewireless power transmitting apparatus 200 and the wireless powerreceiving apparatus 300 may be improved.

The coupling coefficient, which indicates a degree of magnetic couplingbetween a transmitting side coil and a receiving side coil, may have arange of 0 to 1.

The coupling coefficient may vary based on relative position of thetransmitting side coil and the receiving side coil or the distancebetween the transmitting side coil and the receiving side coil.

FIG. 2 is an equivalent circuit diagram of a transmitting induction coilaccording to an embodiment.

As shown in FIG. 2, the transmitting induction coil 210 may include aninductor L1 and a capacitor C1, by which the transmitting induction coil210 may be configured as a circuit having proper inductance andcapacitance values.

The transmitting induction coil 210 may be configured as an equivalentcircuit in which both ends of the inductor L1 are connected to both endsof the capacitor C1. That is, the transmitting induction coil 210 may beconfigured as an equivalent circuit having the inductor L1 and thecapacitor C1 connected in parallel.

The capacitor C1 may be a variable capacitor. As capacitance of thecapacitor C1 is adjusted, impedance matching may be performed.Equivalent circuits of the transmitting resonance coil 220, thereceiving resonance coil 310, and the receiving induction coil 320 mayeach be identical or similar to that shown in FIG. 2. However, thedisclosure is not limited thereto.

FIG. 3 is an equivalent circuit diagram of a power source and a wirelesspower transmitting apparatus according to an embodiment.

As shown in FIG. 3, the transmitting induction coil 210 and thetransmitting resonance coil 220 may include inductors L1 and L2 havinginductance values and capacitors C1 and C2 having capacitance values,respectively.

FIG. 4 is an equivalent circuit diagram of a wireless power receivingapparatus according to an embodiment.

As shown in FIG. 4, the receiving resonance coil 310 and the receivinginduction coil 320 may include inductors L3 and L4 having inductancevalues and capacitors C3 and C4 having capacitance values, respectively.

The rectifier 330 may convert the AC power transferred from thereceiving induction coil 320 into DC power and transfer the DC power tothe load 400.

Specifically, the rectifier 330 may include a rectifier and a smoothingcircuit, which are not shown. In an embodiment, the rectifier may be asilicon rectifier. As shown in FIG. 4, the rectifier may be equivalentas a diode D1. However, the disclosure is not limited thereto.

The rectifier may convert the AC power transferred from the receivinginduction coil 320 into DC power.

The smoothing circuit may remove an AC component from the DC powerconverted by the rectifier to output smooth DC power. In an embodiment,a rectification capacitor C5 may be used as the smoothing circuit asshown in FIG. 4. However, the disclosure is not limited thereto.

The DC power transferred from the rectifier 330 may be DC voltage or DCcurrent. However, the disclosure is not limited thereto.

The load 400 may be any charging battery or device needing DC power. Forexample, the load 400 may be a battery.

The wireless power receiving apparatus 300 may be mounted in anelectronic device, such as a mobile phone, a laptop computer, or amouse, which needs power. Consequently, the receiving resonance coil 310and the receiving induction coil 320 may each have a shape suitable forthe electronic device.

The wireless power transmitting apparatus 200 may exchange informationwith the wireless power receiving apparatus 300 through in bandcommunication or out of band communication.

The in band communication may be a communication for exchanginginformation between the wireless power transmitting apparatus 200 andthe wireless power receiving apparatus 300 using a signal having afrequency used for wireless power transfer. To this end, the wirelesspower receiving apparatus 300 may further include a switch and mayreceive or may not receive the power transmitted from the wireless powertransmitting apparatus 200 through a switching operation of the switch.Consequently, the wireless power transmitting apparatus 200 may detectpower quantity consumed by the wireless power transmitting apparatus 200to recognize an on or off signal of the switch included in the wirelesspower receiving apparatus 300.

Specifically, the wireless power receiving apparatus 300 may changepower quantity absorbed by a resistance element using the resistanceelement and the switch to change power quantity consumed by the wirelesspower transmitting apparatus 200. The wireless power transmittingapparatus 200 may sense change of the consumed power to acquire stateinformation of the load 400. The switch and the resistance element maybe connected in series. In an embodiment, the state information of theload 400 may include information regarding current charge quantity andthe change of charge quantity of the load 400. The load 400 may beincluded in the wireless power receiving apparatus 300.

More specifically, when the switch is opened, power absorbed by theresistance element becomes 0, and thus power consumed by the wirelesspower transmitting apparatus 200 decreases.

When the switch is closed, power absorbed by the resistance elementbecomes greater than 0, and thus power consumed by the wireless powertransmitting apparatus 200 increases. When the wireless power receivingapparatus 300 repeatedly performs the above-described operation, thewireless power transmitting apparatus 200 may detect power consumed bythe wireless power transmitting apparatus 200 to perform digitalcommunication with the wireless power receiving apparatus 300.

According to the above-described operation, the wireless powertransmitting apparatus 200 may receive the state information of the load400 and transmit power suitable therefor.

On the other hand, the wireless power transmitting apparatus 200 mayinclude a resistance element and a switch, by which state information ofthe wireless power transmitting apparatus 200 may be transferred to thewireless power receiving apparatus 300. In an embodiment, the stateinformation of the wireless power transmitting apparatus 200 may includeinformation regarding the maximum power quantity that can be transferredby the wireless power transmitting apparatus 200, the number of wirelesspower receiving apparatuses 300 to which the wireless power transmittingapparatus 200 provides power, and available power quantity of thewireless power transmitting apparatus 200.

Next, out of band communication will be described.

The out of band communication is a communication for exchanginginformation necessary for transferring power using a frequency banddifferent from a resonance frequency band. The wireless powertransmitting apparatus 200 and the wireless power receiving apparatus300 may each be equipped with an out of band communication module, bywhich information necessary for transferring power therebetween may beexchanged. An out of band communication module may be mounted in thepower source 100. However, the disclosure is not limited thereto. In anembodiment, the out of band communication module may use a shortdistance communication scheme, such as Bluetooth, Zigbee, a wirelessLAN, or a near field communication (NFC). However, the disclosure is notlimited thereto.

FIG. 5 is a perspective view showing a wireless power transfer systemaccording to an embodiment.

Referring to FIG. 5, the wireless power transfer system may include acradle 10 and a terminal 20.

The cradle 10 may include the power source and the wireless powertransmitting apparatus shown in FIG. 1. That is, the power source andthe wireless power transmitting apparatus may be mounted in the cradle10. The cradle 10 may have a circular, oval, square, or rectangularshape when viewed from above. However, the disclosure is not limitedthereto.

The top of the cradle 10 may contact one surface of the terminal 20 in asurface contact manner. At least a portion of the top of the cradle 10may have the same shape as the back of the terminal 20. However, thedisclosure is not limited thereto.

The transmitting coils 210 and 220 (see FIG. 1) of the wireless powertransmitting apparatus mounted in the cradle 10 may be disposed in planeopposite to the top of the cradle 10. The transmitting coils 210 and 220may be disposed parallel to the top of the cradle 10 such that power ofthe transmitting coils 210 and 220 can be uniformly transferred to theterminal 20.

The terminal 20 may refer to any electronic device that includes abattery 36 for charging and performs a predetermined electronic functionusing power charged in battery 36. For example, the terminal 20 mayinclude a mobile device, such as a smart phone or a tablet PC, or anelectric home appliance, such as a television, a refrigerator, or awashing machine.

The terminal 20 may include the wireless power receiving apparatus andload shown in FIG. 1. That is, the wireless power receiving apparatusand load may be mounted in the terminal 20.

For charging, the terminal 20 may be placed on the top of the cradle 10.At this time, a back cover 24 of the terminal 20 may contact the top ofthe cradle with a front cover 22 of the terminal 20 upward.Consequently, power may be wirelessly provided from the cradle 10 suchthat the load is charged with the power.

As shown in FIG. 6, the receiving coil 32 and the magnet 30 may bedisposed adjacent to the back of the terminal 20 corresponding to thetop of the cradle 10. The receiving coil 32 may also be disposed inplane opposite to the transmitting coils 210 and 220 of the cradle 10,the top of the cradle 10, and the back cover 24 of the wireless powerreceiving apparatus. Particularly, when the receiving coil 32 of theterminal 20 is positioned parallel to the transmitting coils 210 and 220of the cradle 10, power transfer efficiency of power transferred fromthe transmitting coils 210 and 220 of the cradle 10 to the receivingcoil 32 of the terminal 20 may be maximized.

Hereinafter, the structure of a wireless power transfer system accordingto an embodiment will be described in more detail with reference to FIG.7.

FIG. 7 is a sectional view showing a wireless power transfer systemaccording to an embodiment.

As shown in FIG. 7, the cradle 10 may include a transmitting coil 14 anda first magnet 12. The transmitting coil 14 and the first magnet 12 maybe disposed adjacent to the top of the cradle 10. The transmitting coil14 and the first magnet 12 may be disposed on the same plane.

The transmitting coil 14 may be the transmitting induction coil and/orthe transmitting resonance coil shown in FIG. 1. For example, in aresonance scheme, both the transmitting induction coil and thetransmitting resonance coil may be used. On the other hand, in anelectromagnetic induction scheme, only the transmitting induction coilmay be used.

The transmitting coil 14 may be disposed to surround the first magnet12. The transmitting coil 14 has a number of turns, which are spacedapart from each other. However, the disclosure is not limited thereto.The transmitting coil 14 may be disposed parallel to an imaginaryhorizontal plane. The transmitting coil 14 with the above-describedstructure may have an empty central region.

The first magnet 12 may be disposed in the central region of thetransmitting coil 14. The first magnet 12 may have a thickness equal to,greater than, or less than that of the transmitting coil 14. Thethickness and area of the first magnet 12 may vary depending upon fluxdensity necessary for the first magnet 12 and the occupied area of thefirst magnet 12.

The terminal 20 may include a shielding member 26, a receiving coil 32,and a second magnet 30. The receiving coil 32 and the second magnet 30may be disposed on the same plane.

The receiving coil 32 may be the receiving resonance coil and/or thereceiving induction coil shown in FIG. 1. For example, in the resonancescheme, both the receiving resonance coil and the receiving inductioncoil may be used. On the other hand, in the electromagnetic inductionscheme, only the receiving induction coil may be used.

The receiving coil 32 may be disposed to surround the second magnet 30.The receiving coil 32 has a number of turns, which are spaced apart fromeach other. The receiving coil 32 may be disposed parallel to animaginary horizontal plane. The receiving coil 32 with theabove-described structure may have an empty central region.

The second magnet 30 may be disposed in the central region of thereceiving coil 32. The central region of the receiving coil 32 may beless than that of the transmitting coil 14. However, the disclosure isnot limited thereto. The second magnet 30 may have a thickness equal to,greater than, or less than that of the receiving coil 32. The thicknessand area of the second magnet 30 may vary depending upon flux densitynecessary for the second magnet 30 and the occupied area of the secondmagnet 30.

The second magnet 30 enables approach or contact of the terminal 20 tobe sensed by the cradle 10.

To this end, the cradle 10 may further include a hall sensor 16. Thehall sensor 16 may be disposed between the top of the cradle 10 and thefirst magnet 12. However, the disclosure is not limited thereto. Thehall sensor 16 may be disposed more adjacent to the top of the cradle 10than the first magnet 12. The hall sensor 16 may be disposed in thecradle 10 between the first magnet 12 of the cradle 10 and the secondmagnet 30 of the terminal 20. When there is no terminal 20, the hallsensor 16 senses only flux density of the first magnet 12. On the otherhand, when the terminal 20 approaches the cradle 10, the hall sensor 16may sense flux density of the second magnet 30 as well as flux densityof the first magnet 12. Consequently, the cradle 10 senses flux densityof the first magnet 12 and flux density of the second magnet 30 sensedwhen the terminal 20 is placed on the cradle 10 based on flux density ofthe first magnet 12 sensed when there is no terminal 20. In a case inwhich a change width a of the flux density is equal to or greater than acritical value, it may be determined that the terminal 20 is placed onthe cradle 10 for charging and the terminal 20 may be charged.

In the above embodiment, the hall sensor 16 is described as beingdisposed between the top of the cradle 10 and the first magnet 12.However, the disclosure is not limited thereto. In another embodiment,the hall sensor 16 may be disposed at one side of the first magnet 12under the first magnet 12 or at one side of the transmitting coil 14under the transmitting coil 14.

To this end, the second magnet 30 may be formed of a material causingthe change width a of the flux density which is equal to or greater thanthe critical value. For example, the critical value may be 32 G. In thestandards, a critical value of 40 G may be required.

The second magnet 30 may be formed of an electrical sheet. For example,the electrical sheet may contain 1% to 5% of silicon (Si). However, thedisclosure is not limited thereto. The silicon content of the secondmagnet 30 may be changed to cause a change width a of the flux densitywhich is equal to or greater than the critical value required in thestandards or by customers.

For example, the receiving coil 32 and the second magnet 30 may beattached to the back of the shielding member 26 using an adhesive 28. Onthe shielding member 26 may be disposed a printed circuit board havingelectronic parts, including the power source, an AC power generationunit, and a controller mounted thereon.

The shielding member 26 may shield a magnetic field induced by the coilsuch that the magnetic field cannot affect the electronic parts, therebypreventing malfunction of the electronic parts.

FIG. 8 is a block diagram of a wireless power transfer system accordingto an embodiment.

Referring to FIGS. 5 to 8, the wireless power transfer system mayinclude a cradle 10 and a terminal 20.

The shapes of the cradle 10 and the terminal 20 were previouslydescribed. Hereinafter, circuit components mounted in the cradle 10 andthe terminal 20 will be described.

The cradle 10 may include a power source, an AC power generation unit19, a controller 17, a transmitting coil 14, a first magnet 12, and ahall sensor 16.

The power source may be the power source shown in FIG. 1, and thetransmitting coil 14 may be the transmitting induction coil and/or thetransmitting resonance coil shown in FIG. 1.

The power source may generate AC power or DC power. The power source mayconvert the AC power into first DC power and convert the converted firstDC power into second DC power.

The AC power generation unit 19 may convert power from the power sourceinto AC power under control of the controller 17. The AC power convertedby the AC power generation unit 19 may be transmitted to the terminal 20through the transmitting coil 14.

The controller 17 may control the AC power generation unit 19 based onchanges in intensities of flux densities B1 and B2 detected by the hallsensor 16.

Hereinafter, detection of a voltage signal will be described withreference to FIG. 10.

As shown in FIG. 10, the hall sensor 16 may detect flux density B1 ofthe first magnet 12 included in the cradle 10. In a case in which theterminal 20 is placed on the cradle 10, the hall sensor 16 may detectflux density B2 of the second magnet 30 included in the terminal 20. Inthe figure, the flux density B2 of the second magnet 30 is shown asbeing less than that of the flux density B1 of the first magnet 12.Alternatively, the flux density B2 of the second magnet 30 may be equalto or greater than that of the flux density B1 of the first magnet 12.

The hall sensor 16 may convert the flux density B1 of the first magnet12 and the flux density B2 of the second magnet 30 into electric signalsand provide the electric signals to the controller 17. For example, theelectric signals may be voltage signals. However, the disclosure is notlimited thereto. For example, a flux density of 1 G may be convertedinto a voltage signal of 5 mV. For example, in a case in which the fluxdensity B1 of the first magnet 12 is 10 G, the hall sensor 16 mayconvert the flux density B1, which is 10 G, detected from the firstmagnet 12 into a voltage signal of 50 mV and provide the convertedvoltage signal to the controller 17.

When there is no terminal 20, i.e. when the terminal 20 is located at adistance at which the flux density B2 of the second magnet 30 cannot besensed by the hall sensor 16, a first voltage signal S1 corresponding tothe flux density B1 of the first magnet 12 may be detected.

When the terminal 20 moves into a sensible section P in which the fluxdensity B2 of the second magnet 30 of the terminal 20 can be sensed bythe hall sensor 16 of the cradle 10, a second voltage signal S2corresponding to the sum of the flux density B1 of the first magnet 12and the flux density B2 of the second magnet 30 may be detected.

A boundary point between the distance at which the flux density B2 ofthe second magnet 30 cannot be sensed and the sensible section P may bedefined as an undetectable critical point Q. When the distance betweenthe terminal 20 and the cradle 10 is greater than the undetectablecritical point Q, the flux density B2 of the second magnet 30 cannot besensed by the hall sensor 16. When the distance between the terminal 20and the cradle 10 is less than the undetectable critical point Q, i.e.within the sensible section P, the flux density B2 of the second magnet30 can be sensed by the hall sensor 16.

The second voltage signal S2 may linearly increase as the terminal 20approaches the cradle 10.

The second voltage signal S2 may be saturated at a predetermined pointand then have a uniform level. From the predetermined point, the fluxdensity B2 of the second magnet 30 is maximized. The flux density B2 ofthe second magnet 30 may be maximally maintained within a predetermineddistance and gradually decrease at greater than the predetermineddistance.

When the terminal 20 approaches the cradle 10 and enters a region inwhich the flux density B2 is the maximum, therefore, the second voltagesignal S2 detected by the hall sensor 16 in this region does notincrease any longer and is maintained at a uniform level. That is, sincethe flux density B2 cannot increase to higher than the maximum althoughthe terminal 20 is placed on the cradle 10, the second voltage signal S2corresponding to the sum of the flux density B2 of the second magnet 30and the flux density B1 of the first magnet 12 may be maintained at auniform level.

When the terminal 20 is placed on the cradle 10, i.e. the distancebetween the terminal 20 and the cradle 10 is 0, the second voltagesignal S2 corresponding to the flux density B1 of the first magnet 12and the flux density B2 of the second magnet 30 may be detected as auniform level. In this case, the second voltage signal S2 may be greaterthan the first voltage signal S1.

The difference between the second voltage signal S2 and the firstvoltage signal S1 may be defined as a change width a.

For example, when the change width a between the second voltage signalS2 and the first voltage signal S1 is greater than a predeterminedcritical value, the controller 17 may determine that the terminal 20 isplaced on the cradle 10 and control the AC power generation unit 19 totransmit AC power to the terminal 20 through the transmitting coil 14.

The terminal 230 may include a receiving coil 32, a rectifier 34, abattery 36, and a second magnet 30.

The receiving coil 32 may be the receiving resonance coil and/or thereceiving induction coil shown in FIG. 1. The battery 36 may be the loadshown in FIG. 1.

The receiving coil 32 may receive the AC power provided from thetransmitting coil 14.

The rectifier 34 smoothes the AC power provided from the receiving coil32, removes noise from the AC power, and converts the AC power into DCpower.

The terminal 30 may further include a DC-DC converter (not shown)connected between the rectifier 34 and the battery 36 for converting theDC power converted by the rectifier 34 into rated power or rated voltagerequired by the battery 36.

The terminal 20 may communicate with the terminal 10 through in bandcommunication or out of band communication to provide informationregarding the increase and decrease in intensity of power required bythe terminal 20 and a current charged state of the terminal 20 to thecradle 10.

Although not shown, the terminal 20 may further include a managementmodule for sensing the received AC power or the state of the battery 36such that overpower cannot be supplied to the battery 36 and acontroller for controlling the management module and other components.

FIG. 9 is a flowchart illustrating an operation method of a wirelesspower transfer system according to an embodiment.

Referring to FIGS. 8 and 9, in a case in which the terminal 20 is notplaced on the cradle 10, the controller 17 of the cradle 10 controls thecradle 10 to be operated in a sleep mode in which no AC power is emittedand only a requisite component, such as the hall sensor 16, is driven tominimize current consumption.

The controller 17 receives a first voltage signal S1 corresponding toflux density of the first magnet 12 from the hall sensor 16 throughdriving of the hall sensor 16.

The controller 17 determines whether there is a change of the fluxdensity. That is, the controller 17 determines whether a second voltagesignal S2 greater than the first voltage signal S1 provided by the hallsensor 16 is provided. As the terminal 20 approaches the cradle 10, thesecond voltage signal S2 detected by the hall sensor 16 may increase.The second voltage signal S2 may be a signal having flux density B2 ofthe second magnet 30 as well as flux density B1 of the first magnet 12reflected therein. For example, the second voltage signal S2 may beconverted from the sum of the flux density B1 of the first magnet 12 andthe flux density B2 of the second magnet 30. However, the disclosure isnot limited thereto.

The second voltage signal S2 may increase from the first voltage signalS1. As the terminal 20 approaches the cradle 10, therefore, a changewidth a between the second voltage signal S2 and the first voltagesignal S1 may increase as shown in FIG. 10.

The controller 17 may determine whether the change width a between thesecond voltage signal S2 and the first voltage signal S1 is equal to orgreater than a critical value.

Upon determining that the change width a is equal to or greater than thecritical value, the controller 17 may switch the mode from the sleepmode to a wake-up mode.

The wake-up mode may be an enabling process for transmitting power tothe terminal 20.

In the wake-up mode, the controller 17 performs wireless charging. Thatis, power is provided from the power source under control of thecontroller 17. The AC power generation unit 19 may generate AC powerfrom the power of the power source. The generated AC power may betransmitted to the terminal 20 through the transmitting coil 14.

Hereinafter, an optimal disposition design structure of the secondmagnet 30 included in the terminal 20 will be described.

The receiving coil 32 of the terminal 20 may have a wound coil structure(FIG. 11) or a lead frame coil structure (FIG. 12). The receiving coil32 may be manufactured as a flexible printed circuit board (FPCB). In acase in which the receiving coil 32 is manufactured as the FPCB, thereceiving coil 32 may be manufactured to have the same shape as a leadframe coil. The FPCB is a kind of PCB. Since the FPCB is flexible, theFPCB may be three-dimensionally wired and may be reduced in size andweight. Consequently, the FPCB has attracted attention as a materialcapable of replacing a conventional rigid PCB and has been widely usedin small or middle-sized electronic products, such as a mobile phone, adigital camera, a laptop computer, and a camcorder. In addition, theFPCB has been recently applied to various mobile devices, including asmart phone and a tablet PC.

The greatest difference between a wound coil 32A and a lead frame coil32B is based on presence or absence of pads. That is, the wound coil 32Ahas no pad, whereas the lead frame coil 32B has pads 45 and 47.

The wound coil 32A may be wound from one end 41 by a predeterminednumber of turns such that the diameter of the coil is graduallydecreased and then the other end 43 may be withdrawn near one end 41 ofthe wound coil 32A across the number of turns.

The lead frame coil 32B may have one end 41 connected to a first pad 45and the other end 43 connected to a second pad 47. The lead frame coil32B may be wound from one end 41 by a predetermined number of turns suchthat the diameter of the coil is gradually decreased and then the secondpad 47 may be connected to the other end 43. In this case, the secondpad 47 connected to the other end 43 may be disposed in the coil woundby the number of turns.

As described above, the wound coil 32A and the lead frame coil 32B eachhave an empty central region. The second pad 47 connected to the otherend 43 of the lead frame coil 32B may be disposed in the central regionof the lead frame coil 32B.

It is assumed that the diameter of the central region of the wound coil32A is D3 and the diameter of the central region of the lead frame coil32B is D4.

Since there is no pad in the central region of the wound coil 32A, asecond magnet 30A may have a diameter D1 almost equal to the diameter D3of the central region of the wound coil 32A.

On the other hand, since the second pad 47 is disposed in the centralregion of the lead frame coil 32B, a second magnet 30B may have adiameter D2 less than the diameter D4 of the central region of the leadframe coil 32B.

Consequently, the diameter D1 of the second magnet 30A disposed in thecentral region of the wound coil 32A may be greater than the diameter D2of the second magnet 30B disposed in the central region of the leadframe coil 32B.

FIG. 13 is a view showing flux density based on disposition of thesecond magnet in the lead frame coil structure.

Samples as shown in Table 1 are used for experiments. The thickness ofthe second magnet 30B is 150 mm.

TABLE 1 Thickness of Diameter/Area of A ratio of area of second backcover 24 second magnet magnet 30B to available Sample [mm] 30B [mm/mm²]area [%] #1 0.5 8/50 44 #2 0.6 8/50 44 #3 0.7 8/50 44 #4 0.8 9/64 56 #50.5 11/95  84 #6 0.6 11/95  84 #7 0.7 12/113 100 #8 0.8 12/113 100

The available area, which is an area in which the second magnet 30B maybe disposed, may vary depending upon whether the pad is disposed in thecentral region. Since the second pad 47 is disposed in the center regionof the lead frame coil structure, whereas the second pad 47 is notdisposed in the center region of the wound coil structure, the availablearea of the lead frame coil structure may be less than that of the woundcoil structure. In this case, when the second magnet 30B having the samediameter is disposed, a ratio of the area of the second magnet 30B tothe available area in the lead frame coil structure is greater than thatin the wound coil structure.

In FIG. 13, X1 to X5 indicate diameters of the second magnet 30B. X1indicates that the diameter of the second magnet 30B is 8 mm, and X2indicates that the diameter of the second magnet 30B is 9 mm. Inaddition, X3 indicates that the diameter of the second magnet 30B is 10mm, X4 indicates that the diameter of the second magnet 30B is 11 mm,and X5 indicates that the diameter of the second magnet 30B is 12 mm.

A horizontal axis indicates the thickness of the back cover 24 of theterminal 20, and a vertical axis indicates a voltage value convertedfrom the flux density B2 of the second magnet 30B. The voltage value maybe calculated by multiplying the flux density B2 of the second magnet30B by 5. For example, in a case in which the flux density B2 of thesecond magnet 30B is 30 G, the voltage value may be 150 mV.

In FIG. 13, A1, which is a preferable voltage value required in thestandards, is 200 mV, and A2, which is a recommended voltage valuerequired in the standards, is 160 mV. In order to obtain a preferablevoltage value of 200 mV, it is necessary for the second magnet 30B tohave a flux density B2 of 40 G. In order to obtain a recommended voltagevalue of 160 mV, it is necessary for the second magnet 30B to have aflux density B2 of 32 G.

In order to satisfy the standards, it is necessary to dispose the secondmagnet 30B such that the second magnet 30B has the recommended voltagevalue (160 mV) or more.

As shown in FIG. 13, in a case in which the back cover 24 has athickness of 0.5 mm to 0.8 mm, the second magnet 30B has a voltage valueof more than 160 mV.

In addition, in a case in which the back cover 24 has a thickness of 0.5mm to 0.7 mm, the second magnet 30B has a voltage value of more than 160mV when the second magnet 30B has a diameter of 8 mm to 12 mm.

In a case in which the back cover 24 has a thickness of 0.8 mm, thesecond magnet 30B has a voltage value of more than 160 mV when thesecond magnet 30B has a diameter of 9 mm to 12 mm. However, the secondmagnet 30B has a voltage value of less than 160 mV when the secondmagnet 30B has a diameter of 8 mm.

When the second magnet 30B has a diameter of 12 mm or more, the fluxdensity B2 of the second magnet 30B may increase much more. However, asthe diameter of the second magnet 30B increases, power receivingefficiency may decrease. That is, power receiving efficiency may beimproved only when power transmitted from the cradle 10 is efficientlyreceived. On the other hand, as the diameter of the second magnet 30Bincreases, flux density increases. However, the increasing flux densitydisturbs generation of current due to the receiving coil 32B of theterminal 20. As a result, the terminal 230 may not efficiently receivepower from the cradle 10.

In a case in which the power receiving efficiency of the terminal 20 isguaranteed, therefore, the second magnet 30B may have a diameter of 12mm or more. Even in this case, the maximum diameter of the second magnet30B cannot exceed the diameter obtained based on the available area. Forexample, on the assumption that the available area is 130 mm², a radiusr is 6.43 mm since the available area is 3.14r². Consequently, theavailable area may have a diameter D of 12.86 mm since D=2r.

If the power receiving efficiency of the terminal 20 is not guaranteed,the second magnet 30B may have a diameter of less than 12 mm.

Meanwhile, Table 2 shows disposition standards of the second magnet 30Ain the wound coil structure.

TABLE 2 Thickness of Diameter/Area of A ratio of back cover secondmagnet area of second magnet Sample 24 [mm] 30A [mm/mm²] 30A toavailable area [%] #1 0.5 8/50 22 #2 0.6 8/50 22 #3 0.7 8/50 22 #4 0.89/64 28 #5 0.5 11/95  42 #6 0.6 11/95  42 #7 0.7 12/113 50 #8 0.8 12/11350

As shown in Table 2, the disposition standards of the second magnet 30Ain the wound coil structure are identical to those of the second magnet30B in the lead frame coil structure. As previously described, however,no pad is disposed in the central region of the wound coil 32A since thewound coil 32A has no pad. As a result, the central region of the woundcoil 32A may be utilized only as a disposition space for the secondmagnet 30A. Consequently, the entirety of the central region of thewound coil 32A may be an available area. For this reason, a ratio of thearea of the second magnet 30A to the available area in the wound coilstructure is less than that in the lead frame coil structure. Forexample, as shown in Table 1, a ratio of the area of the second magnet30B to the available area in the lead frame coil structure is 44% to100%, whereas, as shown in Table 2, a ratio of the area of the secondmagnet 30A to the available area in the wound coil structure is 22% to50%.

Although Table 2 does not show experimental data on the flux density B2of the second magnet 30A in the wound coil structure, it is sufficientlyexpected that the flux density B2 of the second magnet 30A in the woundcoil structure may show a tendency similar to the flux density B2 of thesecond magnet 30B in the lead frame coil structure.

FIG. 14 is a view illustrating a polarity arrangement method ofpermanent magnets provided in a wireless power transmitting apparatusand a wireless power receiving apparatus according to an embodiment.

Permanent magnets having polarities (N pole and S pole) may be used asthe magnets according to this embodiment. Generally, provision ofmagnetic force to one surface of a permanent magnet such that onesurface of the permanent magnet has a specific polarity is calledmagnetization. When magnets are disposed in a state in which the samepolarities of the magnets face each other, repulsive force is generatedbetween the magnets. On the other hand, when magnets are disposed in astate in which opposite polarities of the magnets face each other,attractive force is generated between the magnets.

Referring to FIG. 14, polarity magnetized at the top of the first magnet12 provided in the cradle 10 may be different from that magnetized atthe bottom of the second magnet 30 of the terminal 20 facing the top ofthe first magnet 12. For example, the top of the first magnet 12 may bemagnetized as an N pole, and the bottom of the second magnet 30 may bemagnetized as an S pole. On the other hand, the top of the first magnet12 may be magnetized as an S pole, and the bottom of the second magnet30 may be magnetized as an N pole.

When the back cover 24 of the terminal 20 is placed on the top of theterminal 10, therefore, attractive force may be generated between thefirst magnet 12 and the second magnet 30.

When attractive force is generated between the first magnet 12 and thesecond magnet 30, a change width a of the flux density sensed by thehall sensor 16 may be higher than when repulsive force is generatedbetween the first magnet 12 and the second magnet 30. In addition, thedistance between the transmitting coil 14 and the receiving coil 32 maybe reduced due to the attractive force between the first magnet 12 andthe second magnet 30.

Consequently, the hall sensor 16 may more rapidly and accurately sensethat the terminal 20 is placed on the cradle 10. In addition, thedistance between the transmitting coil 14 and the receiving coil 32 maybe reduced due to the attractive force between the first magnet 12 andthe second magnet 30, thereby improving wireless power transferefficiency.

In FIG. 14, the polarities of the first magnet 12 and the second magnet30 are shown as being magnetized at the top and bottom thereof. However,the disclosure is not limited thereto. In another embodiment, as shownin FIG. 15, the magnets may be magnetized in various forms.

FIG. 15 is a view illustrating a magnetization method of magnets appliedto a wireless power transmitting apparatus and a wireless powerreceiving apparatus according to an embodiment.

Hereinafter, a disk type magnet will be described by way of example.However, the disclosure is not limited thereto. The magnet may beconfigured to have a polygonal structure, such as a quadrangular shapeor a diamond-shaped structure, or a donut structure.

Referring to FIG. 15, at least one selected from among a top and bottommagnetization method (1501), a sectional and outer circumferentialmagnetization method (1502), a sectional multi-pole magnetization method(1503), and an outer circumferential multi-pole magnetization method(1504) may be used as a magnetization method according to an embodiment.

In another embodiment, the magnetization method of the magnet applied tothe wireless power transmitting apparatus 200 may be different from thatof the magnet applied to the wireless power receiving apparatus 300. Forexample, the top and bottom magnetization method (1501) may be appliedto the magnet included in the wireless power transmitting apparatus 200,and the sectional and outer circumferential magnetization method (1502)may be applied to the magnet included in the wireless power receivingapparatus 300.

The top and bottom magnetization method (1501) is a method ofmagnetizing a magnet such that the top and bottom of the magnet havedifferent poles.

The sectional and outer circumferential magnetization method (1502) is amethod of magnetizing a magnet such that upper and lower sections andthe outer circumference of the magnet have different poles.

The sectional multi-pole magnetization method (1503) is a method ofdividing the section of a magnet into a plurality of cells andmagnetizing the cells such that neighboring cells have different poles.

The outer circumferential multi-pole magnetization method (1504) is amethod of magnetizing the outer circumference of a magnet such thatdifferent poles are alternately disposed along the outer circumferenceof the magnet.

FIG. 16 is a view illustrating a polarity arrangement method of a firstmagnet 12 and a second magnet 30 in a case in which a magnet applied toan embodiment is magnetized using a sectional and outer circumferentialmagnetization method (1502).

Referring to FIG. 16, the section of the first magnet 12 may bemagnetized with a first polarity, and the outer circumference of thefirst magnet 12 may be magnetized with a second polarity different fromthe first polarity. On the other hand, the section of the second magnet30 may be magnetized with the second polarity, and the outercircumference of the second magnet 30 may be magnetized with the firstpolarity.

For example, a user may incorrectly place the terminal on the cradle 10such that a change width a of the flux density sensed by the hall sensor16 is less than a predetermined critical value. At this time, attractiveforce may be generated between the first magnet 12 and the second magnet30 since the polarity of the outer circumference of the first magnet 12is different from that of the outer circumference of the second magnet30 and the polarity of the section of the first magnet 12 is differentfrom that of the section of the second magnet 30. The distance betweenthe first magnet 12 and the second magnet 30 may be reduced due to thegenerated attractive force. As a result, the change width a of the fluxdensity sensed by the hall sensor 16 may increase to the predeterminedcritical value or more. In addition, wireless power transfer efficiencymay be optimized due to the reduced distance between the first magnet 12and the second magnet 30.

FIG. 17 is a view showing internal components of a wireless powertransmitting apparatus according to another embodiment.

Referring to FIG. 17, a cradle 10 may include a plurality of hallsensors 1711 to 1713, first and second vibration modules 1721 and 1722,and a controller 1730.

In FIG. 17, first to third hall sensors 1711 to 1713 are shown. However,the disclosure is not limited thereto. In another embodiment, a largeror smaller number of hall sensors may be provided based on the size ofthe cradle 10 and a method of embodying the cradle 10.

In addition, only two vibration modules are shown in FIG. 17. However, alarger or smaller number of vibration modules may be provided based onthe size of the cradle 10 and a method of embodying the cradle 10.

In particular, as shown in FIG. 17, it can be seen that polarities of afirst magnet 12 and a second magnet 30 according to this embodiment arearranged to generate attractive force between the magnets.

The first to third hall sensors 1711 to 1713 may each measure a changewidth a of flux density and transfer the measured change width a of theflux density to the controller 1730. At this time, the controller 1730may determine whether to start wireless power transfer based on thechange width a of the flux density measured by each of the first tothird hall sensors 1711 to 1713. In a case in which the change width aof the flux density measured by the second hall sensor 1712 above thefirst magnet 12 exceeds a predetermined first critical value, thecontroller 1730 may determine that the terminal 20 is normally placed onthe cradle 10 and start wireless power transfer. On the other hand, in acase in which the change width a of the flux density measured by thesecond hall sensor 1712 is less than the first critical value and thechange width a of the flux density measured by the first hall sensor1711 is equal to or greater than a predetermined second critical value,the controller 1730 may drive the first vibration module 1721 to reducethe distance between the magnets. As the first vibration module 1721 isdriven, the terminal 20 having the second magnet 30 may move to thefirst magnet 12. Afterward, the change width a of the flux densitymeasured by the second hall sensor 1712 may exceed the first criticalvalue.

At this time, flux density of a magnetic field generated in the firstmagnet 12 may be differently measured by the first hall sensor 1711 andthe second hall sensor 1712 depending upon the distances from the hallsensors to the first magnet 12. Consequently, a critical value for achange width a of flux density, which may be used to determine where theterminal is placed on the cradle 10, may be differently set per hallsensor.

A critical value for a change width a of flux density per hall sensormay be preset based on a measured value of the flux density according tothe distance from the first magnet 12 and the hall sensor in a state inwhich the terminal 20 is not placed on the cradle 10.

In a case in which magnets magnetized with polarities as described aboveare disposed in the cradle 10 and the terminal 20 of the wireless powertransfer system, it is possible to maximize the change width a of theflux density measured by the hall sensor 16 and to minimize the distancebetween the magnets, thereby improving wireless power transferefficiency.

In addition, in a case in which magnets magnetized with polarities asdescribed above are disposed in the cradle 10 and the terminal 20 of thewireless power transfer system, it is possible to use thinner andsmaller magnets, thereby reducing the volume of an electronic deviceequipped with the wireless power transfer system.

In FIGS. 7, 14, and 17, the hall sensor is shown as being disposedbetween the first magnet 12 and the top of the cradle 10. However, thedisclosure is not limited thereto. In another embodiment, the hallsensor may be disposed at one side of the first magnet 12 under thefirst magnet 12 or at one side of the transmitting coil 14 under thetransmitting coil 14.

In another embodiment, the transmitting coil 14 is wound on the outsideof the first magnet 12. However, the disclosure is not limited thereto.In another embodiment, the first magnet 12 may be disposed at the upperend of the transmitting coil 14.

At this time, a predetermined shielding material for minimizing effectsof a magnetic field and an electric field may be used between the firstmagnet 12 and the transmitting coil 14.

Hereinafter, kinds of a magnet applicable to embodiments will bedescribed in brief. A permanent magnet applicable to embodiments mayinclude a neodymium (Nd) magnet consisting of neodymium (Nd), iron (Fe),and boron (B), a ferrite (Fe) magnet consisting of manganese (Mn),cobalt (Co), and nickel (Ni), a rubber magnet consisting of ferritepowder and rubber, an alnico magnet using an alloy of aluminum (A1),nickel (Ni), cobalt (Co), and iron (Fe), and a samarium cobalt (Sm—Co)magnet consisting of samarium (Sm), cobalt (Co), and other rare-earthelements.

The permanent magnet may be manufactured to have various shapes, such asa disk shape, a quadrangular shape, a (circular or quadrangular)countersunk hole shape, a ring shape, a globular shape. In addition,some permanent magnets may be isotropically configured such thatmagnetic force can be generated from one side of each of the magnets.

The method according to the embodiments may be manufactured as a programthat can be executed by a computer and may be stored in recording mediareadable by the computer. Examples of the recording media readable bythe computer may include a read only memory (ROM), a random accessmemory (RAM), a compact disc read only memory (CD-ROM), a magnetic tape,a floppy disk, and an optical data storage device. In addition, therecording media readable by the computer may also be realized in theform of a carrier wave (for example, transmission through the Internet).

The recording media readable by the computer may be distributed tocomputer systems connected to each other through a network such that acode readable by the computer is stored or executed in a distributionmode. In addition, a functional program, code, and code segments forembodying the above method may be easily reasoned by programmers in theart to which the disclosure pertains.

As is apparent from the above description, embodiments have thefollowing effects.

First, embodiments have an effect of providing a wireless powertransmitting apparatus capable of effectively sensing a magnetic fieldof a receiver magnet in a wireless power transfer system.

Second, embodiments have an effect of providing a wireless powertransfer system capable of more effectively sensing a magnetic field ofa receiver using polarities of magnets.

Third, embodiments have an effect of providing a wireless power transfersystem capable of optimizing arrangement between a transmitter and areceiver necessary for wireless power transfer using polarities ofmagnets.

Fourth, embodiments have an effect of providing a wireless powertransfer system capable of vertically and horizontally arranging atransmitting coil of a transmitter and a receiving coil of a receiverusing polarities of magnets, thereby maximizing wireless power transferefficiency.

Fifth, embodiments have an effect of defining polarity arrangement of amagnet provided in a transmitter of a wireless power transfer system,thereby standardizing the structure of a receiver per manufacturer.

Sixth, embodiments have an effect in which it is possible to use thinnerand smaller magnets through polarity arrangement of magnets provided ina transmitter and a receiver of a wireless power transfer system,thereby reducing the volume of an electronic device equipped with thewireless power transfer system.

Effects obtainable from embodiments may not be limited by the abovementioned effects, and other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the disclosure pertains.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A wireless power receiving apparatus forwirelessly receiving power from a wireless power transmitting apparatus,the wireless power receiving apparatus comprising: a receiving coil forreceiving the power; and a first magnet for generating flux densityhaving a predetermined intensity at one side of a face thereof oppositeto the wireless power transmitting apparatus, wherein a second magnetprovided in the wireless power transmitting apparatus and the firstmagnet are disposed such that polarities of the magnets are differentfrom each other at opposite faces thereof, and wherein the receivingcoil is disposed to surround the first magnet.
 2. The wireless powerreceiving apparatus according to claim 1, wherein the receiving coil andthe first magnet are disposed on the same plane.
 3. The wireless powerreceiving apparatus according to claim 1, wherein the first magnet isdisposed in a central region of the receiving coil.
 4. The wirelesspower receiving apparatus according to claim 1, wherein the first magnethas a flux density of 32G or more.
 5. The wireless power receivingapparatus according to claim 1, wherein each magnet has a diameter of 8mm to 12 mm.
 6. The wireless power receiving apparatus according toclaim 1, wherein the first magnet is a permanent magnet magnetized onlyat a face thereof opposite to the wireless power transmitting apparatus.7. The wireless power receiving apparatus according to claim 1, whereinthe first magnet is a permanent magnet magnetized using any one selectedfrom among a top and bottom magnetization method, an outercircumferential magnetization method, a sectional multi-polemagnetization method, and an outer circumferential multi-polemagnetization method.
 8. The wireless power receiving apparatusaccording to claim 1, further comprising: a hall sensor disposed betweenthe first magnet and the second magnet.
 9. The wireless power receivingapparatus according to claim 8, wherein the hall sensor comprises atleast one hall sensor, and the critical value is differently set basedon a distance between each hall sensor and one of the first magnet andthe second magnet.